The purpose of this Core is to provide a common set of state-of-the-art biochemical analyses to Center researchers. The Core laboratory will provide assessments of hypothalamic/pituitary/adrenal axis function, reproductive axis function, antidepressant and antiepileptic drug concentrations to the individual Research Projects of the Center. Accurate measurement of these parameters is imperative to fully characterize each of the clinical model systems of pregnancy (i.e. pregnancy with major depression, pregnancy with epilepsy, pregnancy with bipolar disorder, etc) being investigated by the Center. Accurate determination of drug concentrations (and their metabolites) is also central to the development of PK/PD models and the preclinical investigations being conducted by Center investigators. Having these determinations performed by a central facility using a common set of assay modalities will provide an unprecedented opportunity to compare these models and preclinical investigations with direct clinical data. Additionally, having a Core devoted to these analyses will guarantee high quality assay performance, allow for economies-of-scale in the purchase of assay reagents and technician time, and enable Center investigators to more fully concentrate their efforts on the unique aspects of their particular project.